Quote:
Originally Posted by renault_megane_dci
Noob question (and sorry about it) :
let's assume I feel there is some potential by lowering the rear only to better match the template and improve windscreen angle and that I can lower the bumper at the front to manage pressure differential underneath the car.
Is the only way to alter the car pic on the side ?
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If you lower the rear of the car you alter the inclination of the forebody's (angle-of-attack if you will).In so doing,you alter the pressure gradient and
shearing potential of the flow outside the boundary layer,limiting the amount of momentum delivered into the boundary layer which could trigger premature separation.
There's also a chance that areas of the sides of the car which were 'clean' at the factory inclination might 'catch' air,now that it is moving more obliquely.
You'd want to be very careful.
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I'm not sure about your second question as pertaining to the sides.
If you look straight down on the car from above,their is much potential for plan-view streamlining.As GM did with Impact/EV1 and Honda's 1st-gen Insight.
Again,care must be taken so as not to create adverse pressure spikes which can trigger separation of the boundary layer or transverse shear which might roll up into vorticity.
A technical drawing of the 1957 MG EX 181 is available which shows all views of that land speed record car of Cd 0.12.It's plan -view taper would be a conservative template for streamlining.Honda used such contours with their successive Dream solar racers.
I'm not sure if this answers your question.